1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for recording, a method of manufacturing the same, and a magnetic recording apparatus in which a thin film magnetic head is mounted.
2. Description of the Related Art
In recent years, a magnetic recording apparatus typified by, for example, a hard disk drive is being widely spread. In the field of development of the hard disk drive, in association with improvement in surface recording density of a hard disk as the magnetic recording medium (herein below, simply called “recording medium”), improvement in performance of a thin film magnetic head is demanded. Known recording methods of a thin film magnetic head are a longitudinal recording method in which the orientation of a signal magnetic field is set to an in-plane direction (longitudinal direction) of a recording medium and a perpendicular recording method in which the orientation of a signal magnetic field is set to a direction orthogonal to the surface of a recording medium. At present, the longitudinal recording method is widely used. However, when a market trend accompanying improvement in surface recording density is considered, it is assumed that, in place of the longitudinal recording method, the perpendicular recording method will be regarded as a promising method in future for the following reason. The perpendicular recording method has advantages such that high linear recording density can be assured and a recorded recording medium is not easily influenced by thermal fluctuations.
The main part of a thin film magnetic head of the perpendicular recording method has, for example, a thin film coil for generating a magnetic flux, a magnetic pole layer for executing a recording process by emitting the magnetic flux generated by the thin film coil toward a recording medium, and a return yoke layer for returning the magnetic flux emitted from the magnetic pole layer and magnetized the recording medium.
As thin film magnetic heads of this kind, for example, some thin film magnetic heads in each of which a return yoke layer is disposed on a trailing side of the magnetic pole layer are known (for example, refer to U.S. Pat. No. 4,656,546 and Japanese Unexamined Patent Application Nos. Hei05-325137, Hei06-236526, and 2003-045008). In the thin film magnetic heads, mainly, when a magnetic flux is generated, a part of the magnetic flux emitted from a portion around an edge on the trailing side of the magnetic pole layer, that is, spread components of the magnetic flux to the periphery flow into the return yoke layer, so that spread of the magnetic flux is suppressed. Therefore, in the thin film magnetic heads, as compared with a thin film magnetic head which does not have the return yoke layer, the recording magnetic field gradient near a recording-medium-facing surface (air bearing surface) is sharper, so that an advantage of improved S/N (Signal to Noise) ratio is obtained.
Another example of the known thin film magnetic head in which the return yoke layer is disposed on the trailing side of the magnetic pole layer is a thin film magnetic head in which a portion facing the magnetic pole layer of the return yoke layer is partly projected to the magnetic pole layer side (refer to, for example, Japanese Unexamined Patent Application No. 2002-092820). The thin film magnetic head has an advantage of reduced track edge noise since spread of a magnetic flux emitted from the magnetic pole layer in the track width direction is suppressed when the magnetic flux is returned via the recording medium to the return yoke layer.
To improve recording performance of a thin film magnetic head of the perpendicular recording method, for example, it is necessary to suppress spread of the magnetic flux at the time of recording and to sharpen the gradient of a recording magnetic field as much as possible near the air bearing surface. With respect to this point, for example, the above-described thin film magnetic head in which a part of the return yoke layer is partly projected is very useful. However, considering expected future needs for further improvement in recording performance, it can be said that the configuration of the thin film magnetic head still has room for improvement. In particular, when mass productivity of the thin film magnetic head is considered, it is desired not only to seek a configuration of a thin film magnetic head of which recording performance is expected to be improved but also to establish a concrete manufacturing method capable of mass-producing the thin film magnetic head.